/Engine/Plugins/Runtime/MeshModelingToolset/Source/ModelingComponents/Public/Mechanics/CurveControlPointsMechanic.h
TODO: It is simple to allow the points to be moved arbitrarily, not just inside the plane, if we ever want to use the mechanic somewhere where that is desirable. However, we'd need to do a little more work to allow new points to be added in arbitrary locations.
void SetSnappingEnabled ( bool bOn )